theme 10 – leftovers: meteors and asteroids astr 101 prof. dave hanes
TRANSCRIPT
Theme 10 – Leftovers: Meteors and Asteroids
ASTR 101Prof. Dave Hanes
Meteors: Individual, or in Groups- not “falling stars!”
To Be Precise
Meteoroid = the pebble out in space
Meteor = the luminous event we see (the trail of the “falling star”)
Meteorite = any surviving lump that we find on the ground
What We Are Seeing
Most meteors are small (tiny pebbles, or even grains, of rocky material)
They enter Earth’s atmosphere at very high speed (many tens of km/sec)
Air resistance slows them and heats both the pebble and the column of air – this is what we see, not the pebble itself
Some Can be Very Bright
A Range of Sizes
(‘Pebbles’ burn up!)
Ahnigito (“The Tent”) Meteorite
31 tonnes; fell ~ 10,000 years ago
Duck!
Finding Them on the Ground
Various types:
stony (undistinguished!)
carbonaceous chondrites,
iron (very distinctive!), …
A Good Hunting Ground!
Meteor Showers
Not all meteors come in singly.
Remants of Evaporated Comets
A comet breaks up The rubble gets spread out
Moving ‘Gravel Pits’- and a trick of perspective
The Shower has a‘Radiant’ - hence the name (e.g. the Perseids, in
August)
The Leonids in1833 and 2001
Asteroids
We Can Visit Them(Vesta and Ceres)
Finding New Ones
‘Earth-Crossing’ Orbits
We Do Get Hit![here, about 30,000 years ago]
The Speed is the Key Factor
All of the kinetic energy (the energy of motion) is released when the moving object hits the target.
A 1-gram pebble moving 100 km/sechas as much kinetic energy as a10-ton truck moving along the highway at 100 km/hour
http://www.popularmechanics.com/technology/engineering/gonzo/behold-the-900-mph-supersonic-ping-pong-bazooka-15097897
The Same Basic Physics!http://www.youtube.com/watch?v=Pi-NIeJ26BI
Local Examples
Relatively Recently, in Russia
Very Recently in Chelyabinsk, Russia
Even a ‘miss’ can be quite destructive
http://www.youtube.com/watch?v=dBvotWfR3j4/
Back to Tunguska
How aboutbigger still?